Many structures have been built of many different types of materials and of widely varying sizes and designs for many different purposes and many others are foreseeable. All such structures will have the common design factor of the weight of the materials of which they are built and, if intended to be utilized for more than a very short period of time, must be provided with a foundation which will stably and substantially immovably support the weight of the structure on the material (e.g. soil) underlayment naturally present at the desired location of the structure.
In general, a barrier is also desirable over the natural underlayment which can function as a floor capable of carrying substantial loads. Such a barrier is often provided by a concrete slab which is poured in place within the foundation inner perimeter. The slab may be reinforced to increase the strength thereof and to prevent damage from temperature changes and hydrostatic forces and the like which may occur.
However, if such a slab or other structure is formed within the perimeter of a foundation structure, it will usually be at least imperfectly integral therewith even if some structural connection is provided; allowing differential settling of the slab or other structure relative to the foundation and/or moisture seepage between the foundation and slab or other structure. Further, for some soil types, it may be desirable to have the slab or other structure function as part of the foundation such that the building will essentially “float” on an area of soil which is much increased from the area upon which the foundation, itself, rests. This latter concern requires a substantial degree of structural integration of the foundation and slab or other structure that may not be achieved with high confidence when the foundation and slab are separately formed in situ, as is the current practice. The desired size of a structure may require conventional techniques to be performed in a manner which may compromise the joint functions of the wall foundation and the floor slab to support the building and provide a load bearing barrier.
Additionally, since most such structures are built in response to a recognized or anticipated need, the time required for providing a suitable foundation and slab is an important factor in the building of any structure and may not be adequately satisfied with in-situ construction techniques, particularly in view of the time and labor required for concrete finishing (e.g. to obtain the desired surface finish or texture) and the time required for curing of the concrete to attain sufficient strength for further construction to be performed (usually on the order of several days although concrete will continue to cure and increase in strength over a period of weeks or months). Moreover, at the present time, buildings which are intended to be temporary and/or capable of being relocated or rebuilt while utilizing a minimum of new material and a maximum of previously used structural components (or are of a construction which at least provides that potential) are of particular interest and usually of increased value for that reason.